Some communications systems transmit ancillary data, which can serve different purposes, for example to send information about the status of different elements in the system or to allow changing configuration of devices that are remotely connected. Some systems have a high number of interconnections, so it is desirable not to add more channels, which could be difficult to route, and that would require supplemental pins on the electronic devices.
Filters have been used in existing high-speed connections to carry extra information such as ancillary data on a separate channel or frequency spectrum. These filters however do not perfectly eliminate the deleterious effects of the ancillary data on the high-speed message channel, and reduce the performance of the latter due to information leaking from the ancillary data channel into the high-speed message channel, the leaking information being perceived as noise in the high-speed message channel. Leakage from the message channel into the ancillary data channel can also affect the performance of the ancillary data channel.
A further disadvantage associated with the use of filters relates to the discontinuities associated with the connection of the filters, and the impedance of these circuits, which cause undesirable effects on the high-speed channel.
Transmitting ancillary data also usually requires additional transmitter and receiver circuits for transmission and decoding of the information to be sent and received.
It is desirable to provide a data communications system that overcomes these problems associated with the transmission of ancillary data.